Aluminum alloy can end and body

ABSTRACT

The present invention teaches a process for preparing high strength, improved formability aluminum base alloys suitable for use as can end stock, said high strength aluminum material of the present invention being readily compatible with aluminum can body material. The present invention also teaches an improved aluminum can having ends and body of substantially the same aluminum base alloy, which can as a whole is especially convenient to process in scrap reclamation procedures.

El ite State's atent 1 Setzer et al. Dec. 3, 1974 ALUMINUM ALLOY CAN ENDAND BODY 1795,34] 3/1974 Ostrcm 220m [75] Inventors: William C. Setzer,Hamden; Harvey -P Woodbridge; Joseph Primary ExaminerGeorge T. HallWinter, New Haven, all O C Anorney, Agent, or Firm-Robert H. Bachman[73] Assignee: Swiss Aluminium Ltd., Chippis,

Switzerland 22 Filed: July 5, 1973 [571 ABSTRACT PP No.2 376,740 Thepresent invention teaches a process for preparing Related Us ApplicationData high strength, improved formability aluminum base Divigion of ScrNo 291835 Sc t 25 1972 Pt alloys suitable for use, as can end stock,said high NO 787 248 strength aluminum material of the present mventionbeing readily compatible with aluminum can body ma- [52] U S Cl 220/273terial. The present invention also teaches an improved [5}] ln.t .Cl17/20 aluminum can having ends and y of Substantially 58] Field 148/1 15 A the same aluminum base alloy, which can as a whole is especiallyconvenient to process in scrap reclamation [56] References Citedprocedures UNITED STATES PATENTS 5 Claims, 2 Drawing Figures- 3,672.5356/l972 McGuire 220/54 PATENTE' mac 31914 FIG-l ALUMINUM ALLOY CAN ENDAND BODY This is a division, of application Ser. No. 291,835, filedSept. 25, 1972, now US. Pat. No. 3,787,248.

BACKGROUND OF THE INVENTION It is well known that there has been a rapidgrowth in the use of aluminum cans, especially of the easy open variety.This rapid growth has resulted in a national effort to retrieve andrecycle as many aluminum cans as possible, particularly among publicspirited beverage companies and ecologically minded citizens.

One of the most significant difficulties with recycling most currenteasy open aluminum cans is the fact that different alloys are generallyutilized for the can end and for the can body. For example, alloys 5082or 5182 are commonly used for the can end and alloy 3004 is commonlyused for the can body. Thus, in recycling these two-piece aluminum cans,one must contend with a mixed alloy scrap, which is inconvenient anddifficult to process and in fact highly undesirable.

The can end alloyswith their relatively high magnesium content, forexample, alloys 5082 and 5182, are a major cause of recycling problems.In remelting the cans, the magnesium oxidizes readily and is lost. Inaddition, the oxides can be trapped in the melt and result in inferioringots. On the other hand, the can body alloys, for example, alloy 3004,with a lower magnesium content, have not been successfully used for canends because of low strength and ductility properties. The severeforming requirements necessary to produce a satisfactory can end havenot been met by alloy 3004.

Accordingly, it is a principal object of the present invention toprovide a process for preparing high strength aluminum alloys havingimproved formability suitable for use as can end stock.

It is a further object of the present invention to provide a process asaforesaid which enables the production of aluminum can ends havingsubstantially the same composition as the aluminum can body.

It is a further object of the present invention to provide an improvedaluminumcan wherein the ends and body thereof have substantially thesame composition.

An additional object of the present invention is to provide a processand article as aforesaid which enables convenient recycling of thealuminum can.

Further objects and advantages of the present invention will appearhereinafter.

SUMMARY OF THE INVENTION In accordance with the present invention, ithas now been found that the foregoing objects and advantages may bereadily obtained. The process of the present invention provides a highstrength'aluminum base alloy having improved formability and comprises:

A) providing an aluminum base alloy consisting essentially of from 0.5.2.0 percent manganese, from 0.4 2.0 percent magnesium, balanceessentially aluminum;

B) homogenizing said alloy at a temperature of from 850F to ll50F forfrom 2 hours to 24 hours;

C) rolling said alloy with a starting temperature in the range 650 950F,with a total reduction in excess of 20 percent to a gage of 0.5 inch orabove;

D) further rolling said alloy with a starting temperature in the range400 800F, with a total reduction in excess of 20 percent, preferablyfrom 45 to 85 percent to a gage of 0.100 inch .or above;

E) further rolling said alloy at a starting temperature less than 400F,preferably cold rolling, with a total reduction in excess of 20 percent,preferably 40 percent; and

F) holding said alloy at a temperature between 200 450F for a period oftime of at least five seconds but no greater than defined in thefollowing formula: T( 12 log t) 12,500, wherein Tis the temperature indegrees Kelvin and t is the maximum time in minutes at temperature T.

It is preferred to repeat steps E) and F), optimally a plurality oftimes.

In the preferred embodiment, the alloy is thermally stabilized at atemperature of from 250 to 450F for a period of time of at least fiveseconds but no greater than defined by the formula set forth above,wherein T and t are as defined above. The stabilization treatment may becombined with the standard coating operation in which the can end stockis coated with a polymeric material prior to use. I

The present invention also resides in an improved aluminum can havingends and body thereof of substantially the same composition, namely,both the ends and body thereof consist essentially of from 0.4 2.0percent magnesium, 0.5 2.0 percent manganese, balance essentiallyaluminum, wherein at least one end thereof has a minimum stretch formingheight to diameter ratio of 0.210 and generally 0.242.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 illustrates a fragmentaryperspective view of a sealed container of the present invention; and

FIG. 2 is a sectional view on an exaggerated scale of the tab elementillustrated in FIGQl taken through line 2-2 thereof.

DETAILED DESCRIPTION As indicated hereinabove, the process of thepresent invention attains a great many significant and in factsurprising advantages. A particular advantage of the process of thepresent invention is that it enables the preparation of aluminum canends having substantially the same composition as the aluminum can body.This is a particular advantage in view of the rapid growth and use ofthe easy open can. Thus, the unitary composition of the presentinvention provides ease of recycling and eliminates the necessity forsegregating blanking scrap. These represent considerable economicadvantages. Hence, the process of the present invention enables thepreparation of an improved aluminum can wherein the ends and bodythereof have substantially the same chemical composition, as indicatedhereinabove.

It is a further and surprising advantage of the process of the presentinvention that this process imparts significant improved physicalcharacteristics to the can top material of the present invention. Hence,the aluminum material processing herein is characterized by surprisinglyimproved strength, ductility, formability-and thermal stability. Theimproved characteristics of the can top of the present invention enablethis material to be readily processed into commercial can ends utilizingconventional manufacturing-equipment. This is a particular advantage inview of the large scale use of this equipment. Furthermore, the improvedphysical characteristics of the alloy herein, imparted by the process ofthe present invention, represent a significant and surprising advantageof the present invention. These characteristics will be discussed ingreater detail hereinbelow.

As an example of the foregoing, conventional materials used currentlyfor can ends include aluminum alloy 5182 having the followingcomposition limits: Silicon, up to 0.20 percent; iro'n, up to 0.35percent; copper, up to 0.15 percent; manganese, from 0.20 to 0.50percent; magnesium, from 4.0 to 5.0 percent; chromium, up to 0.10percent; zinc, up to 0.25 percent; titanium, up to 0.10 percent; balancealuminum. The process of the present invention provides the followingfeatures on the alloys processed herein, which have substantially thesame composition as the aluminum can body currently used. in particularreference to aluminum alloy 3004, which has the following compositionlimits: Manganese, from L to 1.5 percent; magnesium, from 0.8 to 1.3percent; zinc, up to 0.25 percent; balance aluminum, the followingrepresents advantages of the processing of the present invention. Theprocessing of the present invention achieves superior stretch formingcharacteristics over the conventionally used alloy 5182. Furthermore, inthe final can end configuration, the 3004 can end processed inaccordance with the present invention requires less load thanconventional 5 l 82 to initiate tab removal and yet still maintain safehandling characteristics in the resultant can end. This represents aparticularly desirable feature since the can may be safely handledduring filling, packing and shipping, and still be more easily opened bythe ultimate consumer. A particular advantage of the material processedin accordance with the present invention is its superior strength,ductility combination over the same material processed in a conventionalmanner. Hence, the process of the present invention permits an alloy,such as 3004, to be readily formed into can ends because of the enhancedductility imparted thereby, and yet the material is still strong enoughto safely contain the pressurized contents.

An additional advantage of the material processed in accordance with thepresent invention is that it achieves superior thermal stability toconventionally processed materials such that a high yield strength canbe maintained after the final thermal treatment. Furthermore, thisenhanced thermal stability permits a broader range of thermal treatmentduring the coating process over conventionally processed material, thatis, higher temperatures for longer times may be utilized whichrepresents an advantage commercially.

An additional and surprising advantage of the process of the presentinvention is that it enables a can end material which is more corrosionresistant than can ends formed from conventional materials such asaluminum alloy 5182. Also, no galvanic corrosion is possible since theentire can utilizes one alloy throughout.

alloy of the present invention preferably contemplates the inclusion ofthe following optional constituents, all of which may be present inamounts as low as 0.001

percent and preferably as low as 0.01 percent; Silicon, up to 0.5percent; iron, up to l percent; copper, up to 0.5 percent; zinc, up to0.5 percent; chromium, up to 0.2 percent; beryllium, up to 0.01 percent;boron, up to 0.01 percent; and titanium, up to 0.2 percent. In additionto the foregoing, other components may be present in an amount of each0.05 percent, total up to 0.20

percent. Naturally, conventional impurities may be contemplated.

In accordance with the present invention, the alumi num alloys utilizedherein may be cast in any desired manner. The particular method ofcasting is not critical and any commercial method may be convenientlyemployed, such as direct chill or tilt mold casting. It is pre ferred toutilize direct chill casting to provide a finely dispersed uniformparticle size of second phase constituents. After casting, ahomogenization or solutionization treatment is utilized for a sufiicientperiod of time to avoid macro-segregation. This homogenization treatmentshould be performed at a temperature from 850F to ll50F and preferablyfrom l000F to ll25F and the ingot should be held at temperature for from2 to 24 hours.

The process of the present invention contemplates a series of rollingsteps, each of which falls within critical temperature limits. The firstrolling step of the present invention is with a starting temperature inthe range of 650 to 950F, with the total reduction in excess of 20percent. Naturally, the total reduction is dependent upon ingot gage,with the material being rolled in this step to a gage of 0.5 inch orabove. This rolling step is intended to break up the cast structure andget the material to a workable gage. i

The material is then further rolled with a starting temperature in therange of- 400 to 800F and with a total reduction in excess of 20percent. The total reduction in this step is preferably from 45 to 85percent and optimally from 50 to 70 percent. The material is rolled inthis step to gage of 0.100 inch or above and preferably to a gage of0.175 to 0.250 inch. This rolling step is particularly critical in thatit has been found that the starting temperature must be kept within theforegoing range in order to insure adequate strength prior to coldrolling.

The material is then further rolled at a starting temperature less than400F, and preferably cold rolled, with a total reduction in this step inexcess of 20 percent and preferably from 40 to 80 percent. The gagerequirements here are dictated by the amount of reduction employed andthe final gage requirements, e.g., the final can end stock gage.

The material is then held at a temperature between 250 and 450F for atleast five seconds, but for a period of time no greater than defined inthe following formula: T 12 log t) 12,500, wherein T is the tempervature in degrees Kelvin and r is the maximum time at As indicatedhereinabove, it has been found that the foregoing process imparts to thealloys herein im'proved strength, ductility, formability and thermalstability so that they can be readily manufactured into easy open canends on a commercial basis in a simple, convenient and expeditiousmanner.

The process of the present invention preferably contemplates a finalthermal stabilizing step. This thermal stabilizing step may be readilyachieved as an inherent feature of the coating process to which thesematerials are conventionally subjected. Conventionally, the coatingprocess comprises coating the can material with a polymeric material,such as an epoxy, polyvinyl chloride or a polyolefin. This step isintended to avoid deleterious reaction between the contents of the canand the aluminum alloy can or can top material. Normally, the coatingand curing process involves a certain holding and elevated temperaturecombination. Thus, the thermal stabilizing step of the present inventioncontemplates holding said material at a temperature of from 250 to 450Ffor a period of time of at least five seconds but no greater than thatwhich is defined by the formula set forth above. Preferably, the holdingtime is from 4 to 24 hours and the preferred temperature is from 250 to375F. Naturally, the optimal holding times and temperatures areinterrelated. The stabilizing treatment is intended to insure uniformproperties throughout the coil and is important in maintaining theseuniform properties. In this step the yield strength properties shouldnot drop more than 50 percent.

Thus, the present invention provides an improved sheet metal product, animproved can end and also an improved aluminum can. As indicatedhereinabove, it

is a particular advantage'of the present invention that substantiallythe same alloy can be utilized for the can ends and body. Thecomposition consists essentially of from 0.4 to 2.0 percent magnesium,0.5 to 2.0 percent manganese and the balance essentially aluminum.Naturally, additives and impurities may be utilized, so that thefollowing limits are contemplated: Silicon, up to 0.5 percent; iron, upto 1.0 percent; copper, up to 0.5 percent; chromium, up to 0.2 percent;zinc, up to 0.5 percent; titanium, up to 0.2 percent; others up to 0.05percent each, total 0.20 percent. Naturally, the present inventioncontemplates variations within the foregoing limits so that identicalalloys need not necessarily be utilized for the can ends and body.

It is a particular advantage of the present invention that it enablesthe use of relatively low magnesium alloys for can end stock, such asalloy 3004. Furthermore, the sheet metal product of the presentinvention has sufficient formability to be processed into a can end,with a minimum stretch forming height to diameter ratio of 0.242. Thesheet metal product of the present invention possesses a minimum yieldstrength of 42,000 psi at 0.2 percent offset and a minimum tensileelongation of 3 percent for a gage of 0.020 inch. Furthermore, the stripcan be thermally treated, for example, at 350F for 13 hours and stillmaintain a minimum yield strength of 42,000 psi. The foregoingrepresents highly advantageous and surprising advantages.

Turning more specifically to the drawings which form a part of thepresent specification, as is shown in FIGS. 1 and 2 thereof, a container1 has a body portion 2 and an end wall 3. The end wall 3 is providedwith a removable portion or tear strip 4 which is defined by scored lineor lines 5. Within the tear strip 4 at one end thereof is afiixed a pulltab or ring pull 6 which is secured to the tear strip 4 by conventionalintegral rivet 7. The can end 3 is secured to the body portion 2 bymeans of fold lock seam 8.

In operation, the can end is opened by pulling on pull tab or ring pull6 which tears along scored lines 5, thus removing the tear strip 4 awayfrom the can end.

As is shown, the ring pull or pull tab is secured to the tear strip bymeans of an integral rivet which is formed directly from the containerend. The fabrication of the integral rivet requires that the can endmaterial be sufficiently formable to be made into a configuration tohold the ring attachment to the can end without fracturing inhandling.The integral rivet is formed in a plurality of operations whichrequire a combination of good strength and ductility, as has beenpointed out hereinabove. A typical method for forming the integral rivetmay be briefly summarized below.

Step 1 is a stretch forming operation in which a hemispherical bubble isproduced vertically downward. The purpose of the formation of thishemispherical bubble is to thin the metal in the central portion of thecan end and thus provide extra metal for forming. In addition, thisreduces the severity of the Step 2 forming operation.

Step 2. In this step a small protrusion is produced vertically upward byforcing the Step 1 bubble in a reverse direction into a smaller dieopening. Thus, the operation in Step 2 is a combination of bending,stretch v forming and drawing.

Step 3. This is the final step. After the Step 2 protrusion is formed,the can end is scored to form the tab or tear strip portion and severalminor protrusions are formed to add buckling stability to the can endwhen the tab or tear strip is opened by the consumer. In this finalstep, the ring pull is placed around the Step 2 protrusion which is thenupset to form the final integral rivet configuration.

As an example, a can end was made in accordance with the foregoingsteps. The Step 1 bubble was 0.080 inch in depth and the finished insidediameter was 0.394 inch. Thus, the height to diameter ratio in this Step1 was 0.203. The maximum metal thinning in this Step 1 was from 0.0128to 0.00975 inch, or a reduction of 23.2 percent. In the Step 2operation, the final protrusion height was 0.066 inch with an insidediameter of 0.0968 inch. The total height to diameter ratio for Step 2was 0.685. After the Step 3 operation, the top portion of the rivet wasseverely thinned in compression approximately from 0.008 to 0.004 inch.

Thus, it can be seen that the sheet metal article of the presentinvention must have a high degree of strength,

" ductility and formability in order to be processed to the can topmaterial of the present invention.

In the formation of can top material from the sheet metal of the presentinvention, the coil of processed metal is first subjected to a standardcoating operation in which the can end stock is coated with a polymericmaterial prior to use, such as an epoxy base resin. The metal may passthrough a continuous line where it is first covered with a solvent resincoating. It then passes through a furnace where the solvent is baked outleaving the resin coating. Metal temperature during the bake cycle isconventionally in excess of 300F for a time period of from one to threeminutes. The coated metal is then fabricatedinto easy open can ends bystamping circular blanks from the coil, forming an end flange to providea locus for attachment to the can body and providing a coating of latexto the flange area for use as a sealant. The curled blanks are thenprocessed as indicated hereinabove to attach the pull tab or ring pullto the can top through the integral rivet. The top with pull tabattachment is then affixed to the can body by means of the curledflange, with the latex acting as a pressure sealant for the system.

The process and article of the present invention will be more readilyunderstandable from a consideratio of the following illustrativeexamples.

EXAMPLE 1 Aluminum alloy 3004 was provided having the com- The materialwas processed in the following manner. The material was homogenized at1075F for 12 hours followed by hot rolling at a starting temperature of800F using l percent reductions per pass from 2.00 to 0.600 inch, with areheat after each reduction at 800F for 5 minutes. The material was thenwarm rolled at a starting temperature of 550F using l0 percentreductions per rolling pass from 0.600 to 0.250 inch, with a reheatafter each pass at 550F for 5 minutes. The material was then cold rolledfrom 0.25 to 0.060 inch using percent rolling reductions per pass. Themetal was then heat treated for 2 hours at 260F followed by cold rollingwith a 10 percent reduction per pass from a gage of 0.060 to 0.030 inch.The material was then heat treated at 260F for 2 hours followed by coldrolling to final gage. The material was then stabilized at 350F for 1hour. The foregoing represents the processing of the present invention.

EXAMPLE ll EXAMPLE III In accordance with this Example, alloy 5182 wasprocessed in the manner set forth below. The alloy had the compositionset forth in Table II below.

TABLE [I Composition Silicon 0.l38% Iron 0.21% Manganese 0.34% Magnesium4.50%

TABLE ll-Continued Composition Chromium 0.59%

Titanium 0.096%

Aluminum Essentially Balance The material was homogenized at a 975F for15 hours followed by hot rolling at 825F to 0.150 inch using a 10percent reduction per pass and reheating at 825F for 5 minutes aftereach pass. The material was then cold rolled from 0.150 to 0.0125 inchand then stabilized at 450F for 15 minutes.\

EXAMPLE IV The material of the present invention processed in accordancewith Example I above has improved yield strength of ductility propertieswhen compared to the conventionally processed material of Example 1]above. The strength to ductility ratio is important in producing a canend since the product must have sufficient strength and be sufficientlyductile to be formed into the integral rivet as set forth hereinabove.In order to determine these properties, standard 2 inches gage lengthtensile tests were performed on samples of material processed inaccordance with Example I and Example II, with the exception that thematerial of Example ll was not given a final stabilizing treatment sincethis would degrade the strength properties. Comparison is made at thesame metal thickness and the same yield strength, ductility was measuredin terms of percent elongation in a standard tensile test, with the testbeing performed at room temperature at a cross-head speed of 0.050 inchper minute. The increase in tensile elongation for the materialprocessed in accordance with the present invention over theconventionally processed material is significant. The results are shownin Table III below.

This example illustrates the improved stretch forming characteristics ofthe material processed in accordance with Example I over the materialprocessed in Example lll. Samples processed in accordance with Example Iand III were tested for stretch formability, a property which iscritical in the formation of the integral rivet. This test was conductedby penetrating the metal with a punch of 0.100 inch diameter until themetal failed. The depth of penetration (H) at failure divided by thepunch diameter (D) is a measure of the stretch forming capability of themetal. The following table shows the stretch forming capability (H/D) ofthe two materials. It can be clearly seen that the material processed inaccordance with the present invention has improved stretch formingcharacteristics.

TABLE IV Material /D EXAMPLE l 0.306 EXAMPLE lll 0.242

EXAMPLE VI This example illustrates that the material processed inaccordance with the present invention has enhanced thermal stabilityover the conventionally processed material of Example II. In thisexample, the samples were processed as indicated in Examples I and II,but without the final stabilization step. The thermal stability wasmeasured by the time that it took to degrade the yield strength to42,000 psi when the samples were held at 350F. From the results shown inTable V below it can be clearly seen that the material processed inaccordance with the present invention has enhanced thermal stabilityover conventionally processed material.

TABLE Vl Material Time at 350F to Reach 42,000 psi Yield StrengthEXAMPLE I 13 Hours EXAMPLE ll 32 Minutes walls having a removableportion with a tab element secured thereto by mans of an integralportion of said end wall, said body portion and end walls havingsubstantially the same composition of an aluminum base alloy consistingessentially of magnesium from 0.4 to 2.0 percent, manganese from 0.5 to2.0 percent, balance essentially aluminum, wherein the end wall havingsaid removable portion has a minimum stretch forming height to diameterratio of 0.210.

2. An aluminum can according to claim 1 containing: Silicon, up to 0.5percent; iron, up to 1 percent; copper, up to 0.5 percent; zinc, up to0.5 percent; chromium, up to 0.2 percent; beryllium, up to 0.01 percent;boron, up to 0.01 percent; titanium, up to 0.2 percent; others each upto 0.05 percent, total up to 0.20 percent.

3. An aluminum can according to claim 1 wherein the end wall having saidremovable portion possesses a minimum yield strength of 42,000 psi at0.2 percent offset and a minimum tensil elongation of 3 percent for agage of 0.020 inch.

4. An easy open can end having means for attachment to a can body andhaving a removable portion with a tab element secured thereto by meansof an integral portion of said end wall, said can end having thecomposition consisting essentially of magnesium from 0.4 to 2.0 percent,manganese from 0.5 to 2.0 percent, balance essentially aluminum, saidcan end having a minimum stretch forming height to diameter ratio of0.210 and having a minimum yield strength of 42,000 psi at 0.2 percentoffset and a minimum tensile elongation of 3 percent for a gage of 0.020inch.

5. An easy open can end according to claim 4 containing: Silicon, up to05 percent; iron, up to 1 percent; copper, up to 0.5 percent; zinc, uptoo 0.5 percent; chrromium, up to 0.2 percent; beryllium, up to 0.01percent; boron, up to 0.01 percent; titanium, up to 0.2 percent; otherseach up to 0.05 percent, total up to 0.20 percent.

. UNITED STATES PATENT CFFICE CERTIFICATE 0F CCRECTICN Patent No. 3,51,7 7 Dated December 3, 197

I nt WILLIAM c. SETZER ET AL.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

In Column 7, line 5 1, after "0.250" the word ---inch--- should beinserted.

In Column 8, line 20, the word "of" should read to---' y InColumn-8,.line 56, the word "Example" should read ---Example.s--.

In Column 10, line 2, the word "mans" should read --means----; 1

In Column 10, line 35, "05" should read -5---; 1

In Column, 10, line 36, the word "to should read --to--;

In Column 10, line 37, the word "chrromium" should read chromium--.

Signed and sealed this 11th day of, March 1975.

(SEAL Attest:

C. MARSHALL DANN RUTH C MASON 7 Commissioner of Patents Attesti gOfficer and Trademarks

1. AN EASY OPEN ALUMINIM CAN HAVING A BODY PORTION AND END WALLS SECUREDTHERETO, WITH ONE OF SAID END WALLS HAVING A REMOVABLE PORTION WITH ATAB ELEMENT SECURED THERETO BY MEANS OF AN INTEGRAAL PORTION OF SAID ENDWALL, SAID BODY PORTION AND END WALLS HAVING SUBSTANTIALLY THE SAMECOMPOSITION OF AN ALUMINUM BASE ALLOY CONSISTING ESSENTIALLY OFMAGNESIUM FROM 0.4 TO 2.0 PERCENT, MANGANESE FROM 0.5 TO 2.0 PERCENT,BALANCE ESSENTIALLY ALUMINUM, WHEREIN THE END WALL HAVING SAID REMOVABLEPORTION HAS A MINIMUM STRETCH FORMING HEIGHT TO DIAMETER RATIO OF 0.210.2. An aluminum can according to claim 1 containing: Silicon, up to 0.5percent; iron, up to 1 percent; copper, up to 0.5 percent; zinc, up to0.5 percent; chromium, up to 0.2 percent; beryllium, up to 0.01 percent;boron, up to 0.01 percent; titanium, up to 0.2 percent; others each upto 0.05 percent, total up to 0.20 percent.
 3. An aluminum can accordingto claim 1 wherein the end wall having said removable portion possessesa minimum yield strength of 42,000 psi at 0.2 percent offset and aminimum tensil elongation of 3 percent for a gage of 0.020 inch.
 4. Aneasy open can end having means for attachment to a can body and having aremovable portion with a tab element secured thereto by means of anintegral portion of said end wall, said can end having the compositionconsisting essentially of magnesium from 0.4 to 2.0 percent, manganesefrom 0.5 to 2.0 percent, balance essentially aluminum, said can endhaving a minimum stretch forming height to diameter ratio of 0.210 andhaving a minimum yield strength of 42,000 psi at 0.2 percent offset anda minimum tensile elongation of 3 percent for a gage of 0.020 inch. 5.An easy open can end according to claim 4 containing: Silicon, up to 05percent; iron, up to 1 percent; copper, up to 0.5 percent; zinc, up too0.5 percent; chrromium, up to 0.2 percent; beryllium, up to 0.01percent; boron, up to 0.01 percent; titanium, up to 0.2 percent; otherseach up to 0.05 percent, total up to 0.20 percent.